Colin Sullivan was the first to invent the use of nasal Continuous Positive Airway Pressure (CPAP) to treat Obstructive Sleep Apnea (OSA), e.g., see U.S. Pat. No. 4,944,310. The treatment generally provides a supply of air or breathable gas from a blower to a patient via an air delivery conduit and a patient interface, such as a full-face or nasal mask or nasal prongs. The air or breathable gas is commonly delivered at a pressure of 3 cm H2O to 25 cm H2O and acts as a splint to hold the airway open during sleep.
Patient compliance and acceptance of CPAP therapy is a major driver of the industry. To address this issue, emphasis has been placed on reducing the size of CPAP systems to enhance the look and feel of the systems for patients. There are three major components in a CPAP system, i.e., a flow generator, an air delivery conduit, and a patient interface. To date, there has been a focus on reducing the size of the flow generator and developing less intrusive patient interfaces. However, there has been very little attention paid to the size of the air delivery conduit, which acts as the interface between the patient interface and the flow generator. For example, there is a Kaerys KXS CPAP machine that is supplied with 15 mm tubing. However, the tubing may only be used for pressures up to 15 cm H2O. In order to effectively increase compliance, all components of a CPAP system should be reduced in size and allow a broad range of pressures to be delivered. A smaller CPAP system also provides for smaller packaging requirements.
The air delivery conduit typically used in CPAP therapy has been medical grade tubing as found in hospitals with an outer diameter of 22 mm and internal diameter of 19 mm. As CPAP therapy is generally conducted in the home, this medical tubing can make users apprehensive in adopting the therapy because the medical tubing can look out of place amongst the environment commonly found in a user's bedroom. In addition, the tubing may be bulky and not easily packed up or organized to preserve the look of a bedroom. Furthermore, the sound caused by the medical tubing as it brushes against linen and the added physical interference as far as drag to the patient interface can cause the user some discomfort. There is no current standard ISO tubing size other than 22 mm outer diameter available for use with CPAP systems across the full flow generator pressure range.
Also, current tubing can communicate airflow but are restrictive in communicating electrical signals. Currently, only external insulation, e.g., in the form of a sock or sheath over the tubing, has been added as an accessory to the tubing to reduce “rain out”, which is the collection of water caused from the humidifier within the tubing.
The problems with using tubing with a smaller bore include the high impedance in the tube to provide the desired pressure at the patient interface. Presently, some flow generators are not able to supply sufficient power for the full pressure range required. Also, there are large pressure swings due to the flow generator not being able to respond quickly enough to changes in pressure. Thus, a need has emerged in the art to address these problems.